Aluminum dipsticks are frequently used to measure the contents of underground storage tanks. Comparison of daily readings with metered pumpage gives an indication of the presence of leaks. Careless operators may drop the dipsticks or, even more irresponsibly, throw the dipsticks down the fill tube, causing damage to the bottom of the tank beneath the fill tube. For tanks made of glass fiber reinforced plastic, prior attempts to prevent damage from dipsticks have included installing steel plates at the bottom of the tank beneath the fill tube and pouring rubberized epoxy resin down the fill tube.
Because contractors frequently install the fill tube in other than the intended fitting, some companies order metal plates under all fittings at the time an order is placed for a tank. The different plate specifications render it difficult to maintain a line of standard tanks.